Armenians hoped Yanikian's trial would provide a vehicle for proving the massacres in a court of law, while there were still surviving witnesses. Yanikian took the Armenian Genocide witness stand, accompanied by his friend and interpreter, Santa Barbaran Aram Saroyan, the uncle of famous author William Saroyan. Yanikian told of his 26 family members killed in the massacres, and how he watched in hiding as marauding Turks slit his brother's throat. Finally, he said that he killed the Turkish diplomats as representatives of the "government that had massacred his people".

He was sentenced to life in prison in July 1973 and paroled in 1984, over the objection of the Turkish government.[2]

After Yanikian's death, District Attorney David D. Minner wrote: "Looking back, I regret that I did not allow the genocide to be proven. Not because Yanikian should have gone free, but because history's darkest chapters - its genocides - should be exposed, so their horrors are less likely to be repeated".[2]